In a semiconductor manufacturing process, a specified resist pattern is formed on a substrate, e.g., a semiconductor wafer, by performing a photolithography process that includes a resist coating step in which a resist film is formed by supplying of a resist liquid as a processing liquid onto a surface of the substrate kept on a horizontal plane while rotating the substrate about a vertical axis, a heating (pre-baking) step for evaporating and removing a solvent remaining within the resist film after coating the resist liquid, an exposing step for exposing the resist film in a specified pattern, a heating (post-exposure baking) step for inducing a chemical reaction within the resist film after exposure and a developing step for developing the exposed resist film.
Conventionally, in the photolithography process, a processing system in which an exposure apparatus is connected to coating and developing apparatuses is used.
In a photoresist process performed in the processing system, a liquid processing through the use of a spin coating method is generally performed. As a conventional apparatus for performing this kind of liquid processing, there is known a liquid processing apparatus that includes a substrate holding unit arranged within a processing cup having an open top end and configured to horizontally hold a substrate, a rotating mechanism for rotating the substrate holding unit about a vertical axis, a processing liquid supply unit for supplying a processing liquid on the surface of the substrate, a suction means for sucking an unnecessary atmospheric gas within the processing cup through an exhaust port at the bottom of the processing cup, and an intake port for drawing an ambient air into the processing cup.
In the conventional technology, the intake port for drawing an ambient air into the processing cup and the exhaust port for discharging a gas out of the processing cup are formed in the processing cup. For that reason, an exhaust flow path is formed within the processing cup. Consequently, the mist generated from the liquid process (coated film forming process) can be discharged even with a small suction force.
In recent years, however, the diameter of a substrate has increased, and a substrate of 450 mm in diameter is used in place of a conventional substrate of 300 mm in diameter. When the substrate of 450 mm in diameter is subjected to the liquid process (coated film forming process), it is expected that, in the structure of the conventional liquid processing apparatus, the processing cup exhaust flow rate required to prevent the mist generation is increased approximately twice in terms of the conventional processing ratio. The amount of air to be supplied into the processing cup to secure the internal pressure of the liquid processing apparatus is also increased like the processing cup exhaust flow rate. Accordingly, there is likelihood that the factory power consumption that accounts for the operation cost of the liquid processing apparatus becomes higher.
In the conventional technology, however, since the unnecessary atmospheric gas generated within the processing cup and the ambient air drawn from the intake port are discharged to the factory outside the liquid processing apparatus by the suction force of the suction means installed in the exhaust flow path connected to the exhaust port, the amount of the gas discharged to the factory does not grow smaller. This may make it impossible to reduce the factory power consumption that accounts for the operation cost of the liquid processing apparatus.